Bioelectrocatalysis　presents　a　promising　strategy　for　sustainable　nitrogen　(N2)　fixation　to　ammonia　(NH3),　yet　the　interplay　between　conductive　materials　and　extracellular　polymeric　substances　(EPS)　in　biofilms　remains　underexplored.　Here,　we　demonstrate　that　boron　carbide　(B4C900)　synergizes　with　EPS　to　optimize　bioelectrocatalytic　nitrogen　fixation　in　Pseudomonas　stutzeri　A1501.　The　addition　of　B4C900　enhanced　NH3　production　by　164.41　%,　driven　by　a　38　%　increase　in　tightly　bound　EPS　secretion　and　elevated　electron-accepting　(0.076　±　0.004　μmol　e-)　and　electron-donating　capacities　(0.017　±　0.001　μmol　e-).　Transcriptomic　analyses　revealed　B4C900-mediated　upregulation　of　riboflavin　and　cytochrome　c　biosynthesis　pathways　within　EPS,　enriching　redox-active　mediators　critical　for　electron　shuttling.　Concurrently,　B4C900＇s　intrinsic　conductivity　facilitated　direct　electron　transport　across　the　abiotic-biotic　interface.　This　dual　mechanism　-　enhancing　EPS-mediated　redox　activity　and　establishing　conductive　electron　transfer　pathways　-　effectively　reduced　interfacial　resistance　and　upregulated　energy　metabolism　genes,　including　those　associated　with　ATP　synthase　and　the　tricarboxylic　acid　(TCA)　cycle.　Our　findings　establish　EPS　as　a　pivotal　mediator　in　conductive　material-driven　systems,　offering　a　blueprint　for　efficient　N2-to-NH3　conversion　and　advancing　bioelectrocatalytic　design　principles.　©　2025　Elsevier　Ltd.　All　rights　are　reserved,　including　those　for　text　and　data　mining,　AI　training,　and　similar　technologies.